DESCRIPTION: (Applicant's Abstract) In this project we propose to develop a novel mass spectrometric method, Charge Reduction (CR) Electrospray Ionization (ESI) Mass Spectrometry (MS), for the analysis of enzymatic DNA sequencing reactions. A nanospray Charge Reduction source will be constructed and interfaced with a commercial Electrospray Time-of-Flight (ESI-TOF) instrument. This source will utilize the emitting radioisotope 210Po to ionize the source bath gas, producing ions which in turn neutralize the charges present on the ions generated in the ESI process. This charge neutralization process will greatly reduce the complexity of the mass spectra obtained in ESI-MS from large biopolymers such as DNA, thereby enabling the mass spectrometric analysis of biopolymer mixtures which are otherwise too complex to be useful. It is anticipated that the ability to reduce the number of charge states produced in the electrospray method, coupled with the intrinsic speed and accuracy of mass spectrometric analysis, will provide a viable route to the rapid mass spectrometric analysis of Sanger sequencing reactions in seconds, a dramatic improvement over the capabilities of electrophoretic methods.